2 x 12" (30cm) Pieces of Aluminium track are screwed directly into the walls where you would like your shelf to be. Then you slide the trianglar Glass Shelf (curved edge facing outwards) into the wall mounted tracks and just tighten the support screws on the under side of the rail. Glass shelf is 6mm in thickness. A choice of a White or Silver wall bracket is available, please specify which colour you require upon ordering.